Fluorinated surfactants are widely used in the manufacture of fluoropolymers (and copolymers) in aqueous media. Though chiefly used in the manufacture of fluoropolymer dispersions and of the dry, solid polymers derived therefrom, they are also commonly employed in the manufacture of slurry-(the so-called granular-) type polymer as well, as described, for example, for the polymerization of tetrafluoroethylene (TFE) in U.S. Pat. Nos. 3,245,972; 3,629,219, 3,855,191, and 4,189,551. Chief among the fluorinated surfactants generally used are perfluoroalkanoates, especially perfluorooctanoate, usually in the form of the ammonium salt (APFO), although alkali metal salts and even the corresponding free acid may alternatively be used.
These fluorinated surfactants are intrinsically valuable, but their recovery is difficult because their concentrations in spent polymerization media are relatively low. Furthermore, the surfactants consist of molecules having more-or-less distinct polar and non-polar portions, so that they tend to "bridge" ordinarily immiscible media such as might otherwise be used for their separation, as, for example, by liquid-liquid extraction. In addition, the surfactants have pronounced, and generally undesirable, foaming tendencies, especially in aqueous media.
Despite these difficulties, recovery of the surfactants is desirable because the disposal of spent reaction mixtures by acceptable means is difficult.
It is desirable to provide a process for recovery of the surfactants which employs common, inexpensive inorganic reagents and a simple organic solvent, thereby avoiding the complexity of such techniques as ion exchange for effecting the separation of the surfactants, which overcomes foaming by appropriate choices of media and conditions, especially of pH level, and which can be carried out at atmospheric pressure, and at ambient temperature.